The present invention relates generally to dynamoelectric machines and more particularly to improved methods and apparatus for inserting windings into dynamoelectric machine stator assemblies.
Currently employed schemes for positioning windings in magnetic cores of stator assemblies include the hand-placement of coils into stator cores; machine winding of coils directly in the cores; and various schemes for axially inserting coils into the cores in varying degrees of automation.
Exemplary automated approaches for the axial insertion of coils into magnetic cores include U.S. Pat. No. 2,432,267 (Adamson), 2,934,099 (Mason), 3,324,536 (Hill), 2,836,204 (Mason), and 3,528,170 (Duff et al); and the entire disclosures of these patents are incorporated herein by reference. It is the automated insertion of prewound coils as typified by these patents rather than manual insertion or inslot winding techniques with which the present invention is primarily concerned.
Coil insertion techniques are known in a variety of forms. For example, a single pole group (the set of coils forming a single pole for a dynamoelectric machine) may be wound and placed in stator core slots and thereafter the windings for another pole created and positioned in the slots of the stator core. In other situations, the entire multiple pole winding may be inserted into a stator core in a single pass and sometimes both the main or running windings as well as the auxiliary or start winding are placed in the stator core by a single coil insertion operation. Common to all of these coil injection techniques is the feature that leading end turn coil portions are moved through the stator core bore with the side turn portions of those coils trailing freely behind and passing axially into coil accommodating slots of the core.
In known prior art techniques for inserting coils into slots of a stator core, an inserting device retains portions of end turns of the coils within tooling thereof and axially moves these portions through a bore of the stator core. By axially moving the retained portions through the bore, side turn portions and trailing end turn portions of the coils are also moved but they usually hang freely about the inserting tooling during their approach to the core. With the side turns of the coils trailing in a freely hanging manner, the plurality of turns of each coil often occupy a substantially greater area than the area of a slot into which they are to be inserted. Furthermore, freely hanging side turns of the coils are almost inevitably not in alignment with the axial extending slots into which they are to be moved. Thus, the forced accommodation and alignment of the side turns with their respective slots causes an enormous pressure to be exerted on both the insulating material utilized to separate the winding turns of the coils from the magnetic core and on the magnet wire insulation (i.e., "enamel") itself. The insulating material for the electrical separation of the winding turns and the magnetic core may take the form of a coating such as, for example, an epoxy material disposed along at least the interior surface of the respective slots into which the turns are to be inserted. In other forms, the insulating material may take the form of a so-called slot liner which may comprise a sheet of insulating material such as, for example, paper or polyethylene terephalate which is available under the tradename "MYLAR" of E. I. DuPont de Nemours & Company. The slot liner is configured to conform to interior surfaces of the slots and may be provided with cuffs or tabs extending axially beyond the core faces to engage the faces and thereby prevent movement of the slot liner within the slot and also increase the separation between the magnet wire and slot edges or "corners".
The forced accommodation and alignment of the plurality of winding turns during their movement into their respective slots of the magnetic core and the resulting pressures or forces created thereby, may cause damage to the insulating material which is electrically separating the turns from the magnetic core as well as the wire insulation. The likelihood of damage to the insulating material is particularly acute along edges of the slots at slot entrances interfacing with a face of the core and into which side turns of the coils are initially moved into the slots. This insulation damage may take the form of insulation fatigue, tears, or other types of failures wherein the insulating material is sufficiently damaged so as to reduce or destroy the electrical separation between the winding turns and the magnetic core. Further, in certain types of machines, the insertion of particular coils may cause an increased likelihood of damage to insulating material than the insertion of the other coils. For example, in inserting the windings for a distributively wound two pole machine, the outer coils for each pole group may typically have a greater number of turns which must be forced or squeezed into a configuration so as to allow disposing of the side turns thereof into their respective slots of the core.
Accordingly, a general object of the present invention is to provide new and improved methods and apparatus for inserting coils into a dynamoelectric machine stator assembly which eliminate or minimize deficiencies and problems encountered heretofore as discussed hereinabove.
A more specific object of the present invention is to provide new and improved methods and apparatus for axially inserting coils into a dynamoelectric machine stator assembly which reduce the likelihood of damage to the insulation system of the stator assembly during such coil insertion processes.
Another object of the present invention is to provide new and improved methods and apparatus for axially inserting coils into slots of a stator assembly core in which freely hanging portions of the coils being inserted are guided into respective slots of the magnetic core.
Still another object of the present invention is to provide new and improved methods and apparatus for reducing the probability of damage to the insulation system of a stator assembly during insertion of coils therein in which freely hanging portions of the coil are displaced inwardly twoard a bore of the stator assembly prior to insertion into their respective slots.
A further object of the present invention is to provide new and improved methods and apparatus for minimizing damage to the insulation system of a stator assembly during a coil insertion process in which portions of the coils are circumferentially displaced relative to a face of the magnetic core.